xref: /freebsd/sys/cddl/dev/sdt/sdt.c (revision 43faedc1339a9624c7acedb7f3e5624e64da5b99)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  *
21  * Portions Copyright 2006-2008 John Birrell jb@freebsd.org
22  *
23  * $FreeBSD$
24  *
25  */
26 
27 /*
28  * This file contains a reimplementation of the statically-defined tracing (SDT)
29  * framework for DTrace. Probes and SDT providers are defined using the macros
30  * in sys/sdt.h, which append all the needed structures to linker sets. When
31  * this module is loaded, it iterates over all of the loaded modules and
32  * registers probes and providers with the DTrace framework based on the
33  * contents of these linker sets.
34  *
35  * A list of SDT providers is maintained here since a provider may span multiple
36  * modules. When a kernel module is unloaded, a provider defined in that module
37  * is unregistered only if no other modules refer to it. The DTrace framework is
38  * responsible for destroying individual probes when a kernel module is
39  * unloaded; in particular, probes may not span multiple kernel modules.
40  */
41 
42 #include <sys/cdefs.h>
43 #include <sys/param.h>
44 #include <sys/systm.h>
45 
46 #include <sys/conf.h>
47 #include <sys/eventhandler.h>
48 #include <sys/kernel.h>
49 #include <sys/limits.h>
50 #include <sys/linker.h>
51 #include <sys/linker_set.h>
52 #include <sys/lock.h>
53 #include <sys/lockstat.h>
54 #include <sys/malloc.h>
55 #include <sys/module.h>
56 #include <sys/mutex.h>
57 #include <sys/queue.h>
58 #include <sys/sdt.h>
59 
60 #include <sys/dtrace.h>
61 #include <sys/dtrace_bsd.h>
62 
63 /* DTrace methods. */
64 static void	sdt_getargdesc(void *, dtrace_id_t, void *, dtrace_argdesc_t *);
65 static void	sdt_provide_probes(void *, dtrace_probedesc_t *);
66 static void	sdt_destroy(void *, dtrace_id_t, void *);
67 static void	sdt_enable(void *, dtrace_id_t, void *);
68 static void	sdt_disable(void *, dtrace_id_t, void *);
69 
70 static void	sdt_load(void);
71 static int	sdt_unload(void);
72 static void	sdt_create_provider(struct sdt_provider *);
73 static void	sdt_create_probe(struct sdt_probe *);
74 static void	sdt_kld_load(void *, struct linker_file *);
75 static void	sdt_kld_unload_try(void *, struct linker_file *, int *);
76 
77 static MALLOC_DEFINE(M_SDT, "SDT", "DTrace SDT providers");
78 
79 static dtrace_pattr_t sdt_attr = {
80 { DTRACE_STABILITY_EVOLVING, DTRACE_STABILITY_EVOLVING, DTRACE_CLASS_COMMON },
81 { DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_UNKNOWN },
82 { DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_ISA },
83 { DTRACE_STABILITY_EVOLVING, DTRACE_STABILITY_EVOLVING, DTRACE_CLASS_COMMON },
84 { DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_ISA },
85 };
86 
87 static dtrace_pops_t sdt_pops = {
88 	sdt_provide_probes,
89 	NULL,
90 	sdt_enable,
91 	sdt_disable,
92 	NULL,
93 	NULL,
94 	sdt_getargdesc,
95 	NULL,
96 	NULL,
97 	sdt_destroy,
98 };
99 
100 static TAILQ_HEAD(, sdt_provider) sdt_prov_list;
101 
102 static eventhandler_tag	sdt_kld_load_tag;
103 static eventhandler_tag	sdt_kld_unload_try_tag;
104 
105 static void
106 sdt_create_provider(struct sdt_provider *prov)
107 {
108 	struct sdt_provider *curr, *newprov;
109 
110 	TAILQ_FOREACH(curr, &sdt_prov_list, prov_entry)
111 		if (strcmp(prov->name, curr->name) == 0) {
112 			/* The provider has already been defined. */
113 			curr->sdt_refs++;
114 			return;
115 		}
116 
117 	/*
118 	 * Make a copy of prov so that we don't lose fields if its module is
119 	 * unloaded but the provider isn't destroyed. This could happen with
120 	 * a provider that spans multiple modules.
121 	 */
122 	newprov = malloc(sizeof(*newprov), M_SDT, M_WAITOK | M_ZERO);
123 	newprov->name = strdup(prov->name, M_SDT);
124 	prov->sdt_refs = newprov->sdt_refs = 1;
125 
126 	TAILQ_INSERT_TAIL(&sdt_prov_list, newprov, prov_entry);
127 
128 	(void)dtrace_register(newprov->name, &sdt_attr, DTRACE_PRIV_USER, NULL,
129 	    &sdt_pops, NULL, (dtrace_provider_id_t *)&newprov->id);
130 	prov->id = newprov->id;
131 }
132 
133 static void
134 sdt_create_probe(struct sdt_probe *probe)
135 {
136 	struct sdt_provider *prov;
137 	char mod[DTRACE_MODNAMELEN];
138 	char func[DTRACE_FUNCNAMELEN];
139 	char name[DTRACE_NAMELEN];
140 	const char *from;
141 	char *to;
142 	size_t len;
143 
144 	if (probe->version != (int)sizeof(*probe)) {
145 		printf("ignoring probe %p, version %u expected %u\n",
146 		    probe, probe->version, (int)sizeof(*probe));
147 		return;
148 	}
149 
150 	TAILQ_FOREACH(prov, &sdt_prov_list, prov_entry)
151 		if (strcmp(prov->name, probe->prov->name) == 0)
152 			break;
153 
154 	KASSERT(prov != NULL, ("probe defined without a provider"));
155 
156 	/* If no module name was specified, use the module filename. */
157 	if (*probe->mod == 0) {
158 		len = strlcpy(mod, probe->sdtp_lf->filename, sizeof(mod));
159 		if (len > 3 && strcmp(mod + len - 3, ".ko") == 0)
160 			mod[len - 3] = '\0';
161 	} else
162 		strlcpy(mod, probe->mod, sizeof(mod));
163 
164 	/*
165 	 * Unfortunately this is necessary because the Solaris DTrace
166 	 * code mixes consts and non-consts with casts to override
167 	 * the incompatibilies. On FreeBSD, we use strict warnings
168 	 * in the C compiler, so we have to respect const vs non-const.
169 	 */
170 	strlcpy(func, probe->func, sizeof(func));
171 	if (func[0] == '\0')
172 		strcpy(func, "none");
173 
174 	from = probe->name;
175 	to = name;
176 	for (len = 0; len < (sizeof(name) - 1) && *from != '\0';
177 	    len++, from++, to++) {
178 		if (from[0] == '_' && from[1] == '_') {
179 			*to = '-';
180 			from++;
181 		} else
182 			*to = *from;
183 	}
184 	*to = '\0';
185 
186 	if (dtrace_probe_lookup(prov->id, mod, func, name) != DTRACE_IDNONE)
187 		return;
188 
189 	(void)dtrace_probe_create(prov->id, mod, func, name, 1, probe);
190 }
191 
192 /*
193  * Probes are created through the SDT module load/unload hook, so this function
194  * has nothing to do. It only exists because the DTrace provider framework
195  * requires one of provide_probes and provide_module to be defined.
196  */
197 static void
198 sdt_provide_probes(void *arg, dtrace_probedesc_t *desc)
199 {
200 }
201 
202 static void
203 sdt_enable(void *arg __unused, dtrace_id_t id, void *parg)
204 {
205 	struct sdt_probe *probe = parg;
206 
207 	probe->id = id;
208 	probe->sdtp_lf->nenabled++;
209 	if (strcmp(probe->prov->name, "lockstat") == 0)
210 		lockstat_enabled++;
211 }
212 
213 static void
214 sdt_disable(void *arg __unused, dtrace_id_t id, void *parg)
215 {
216 	struct sdt_probe *probe = parg;
217 
218 	KASSERT(probe->sdtp_lf->nenabled > 0, ("no probes enabled"));
219 
220 	if (strcmp(probe->prov->name, "lockstat") == 0)
221 		lockstat_enabled--;
222 	probe->id = 0;
223 	probe->sdtp_lf->nenabled--;
224 }
225 
226 static void
227 sdt_getargdesc(void *arg, dtrace_id_t id, void *parg, dtrace_argdesc_t *desc)
228 {
229 	struct sdt_argtype *argtype;
230 	struct sdt_probe *probe = parg;
231 
232 	if (desc->dtargd_ndx >= probe->n_args) {
233 		desc->dtargd_ndx = DTRACE_ARGNONE;
234 		return;
235 	}
236 
237 	TAILQ_FOREACH(argtype, &probe->argtype_list, argtype_entry) {
238 		if (desc->dtargd_ndx == argtype->ndx) {
239 			desc->dtargd_mapping = desc->dtargd_ndx;
240 			if (argtype->type == NULL) {
241 				desc->dtargd_native[0] = '\0';
242 				desc->dtargd_xlate[0] = '\0';
243 				continue;
244 			}
245 			strlcpy(desc->dtargd_native, argtype->type,
246 			    sizeof(desc->dtargd_native));
247 			if (argtype->xtype != NULL)
248 				strlcpy(desc->dtargd_xlate, argtype->xtype,
249 				    sizeof(desc->dtargd_xlate));
250 		}
251 	}
252 }
253 
254 static void
255 sdt_destroy(void *arg, dtrace_id_t id, void *parg)
256 {
257 }
258 
259 /*
260  * Called from the kernel linker when a module is loaded, before
261  * dtrace_module_loaded() is called. This is done so that it's possible to
262  * register new providers when modules are loaded. The DTrace framework
263  * explicitly disallows calling into the framework from the provide_module
264  * provider method, so we cannot do this there.
265  */
266 static void
267 sdt_kld_load(void *arg __unused, struct linker_file *lf)
268 {
269 	struct sdt_provider **prov, **begin, **end;
270 	struct sdt_probe **probe, **p_begin, **p_end;
271 	struct sdt_argtype **argtype, **a_begin, **a_end;
272 
273 	if (linker_file_lookup_set(lf, "sdt_providers_set", &begin, &end,
274 	    NULL) == 0) {
275 		for (prov = begin; prov < end; prov++)
276 			sdt_create_provider(*prov);
277 	}
278 
279 	if (linker_file_lookup_set(lf, "sdt_probes_set", &p_begin, &p_end,
280 	    NULL) == 0) {
281 		for (probe = p_begin; probe < p_end; probe++) {
282 			(*probe)->sdtp_lf = lf;
283 			sdt_create_probe(*probe);
284 			TAILQ_INIT(&(*probe)->argtype_list);
285 		}
286 	}
287 
288 	if (linker_file_lookup_set(lf, "sdt_argtypes_set", &a_begin, &a_end,
289 	    NULL) == 0) {
290 		for (argtype = a_begin; argtype < a_end; argtype++) {
291 			(*argtype)->probe->n_args++;
292 			TAILQ_INSERT_TAIL(&(*argtype)->probe->argtype_list,
293 			    *argtype, argtype_entry);
294 		}
295 	}
296 }
297 
298 static void
299 sdt_kld_unload_try(void *arg __unused, struct linker_file *lf, int *error)
300 {
301 	struct sdt_provider *prov, **curr, **begin, **end, *tmp;
302 
303 	if (*error != 0)
304 		/* We already have an error, so don't do anything. */
305 		return;
306 	else if (linker_file_lookup_set(lf, "sdt_providers_set", &begin, &end,
307 	    NULL))
308 		/* No DTrace providers are declared in this file. */
309 		return;
310 
311 	/*
312 	 * Go through all the providers declared in this linker file and
313 	 * unregister any that aren't declared in another loaded file.
314 	 */
315 	for (curr = begin; curr < end; curr++) {
316 		TAILQ_FOREACH_SAFE(prov, &sdt_prov_list, prov_entry, tmp) {
317 			if (strcmp(prov->name, (*curr)->name) != 0)
318 				continue;
319 
320 			if (prov->sdt_refs == 1) {
321 				if (dtrace_unregister(prov->id) != 0) {
322 					*error = 1;
323 					return;
324 				}
325 				TAILQ_REMOVE(&sdt_prov_list, prov, prov_entry);
326 				free(prov->name, M_SDT);
327 				free(prov, M_SDT);
328 			} else
329 				prov->sdt_refs--;
330 			break;
331 		}
332 	}
333 }
334 
335 static int
336 sdt_linker_file_cb(linker_file_t lf, void *arg __unused)
337 {
338 
339 	sdt_kld_load(NULL, lf);
340 
341 	return (0);
342 }
343 
344 static void
345 sdt_load()
346 {
347 
348 	TAILQ_INIT(&sdt_prov_list);
349 
350 	sdt_probe_func = dtrace_probe;
351 
352 	sdt_kld_load_tag = EVENTHANDLER_REGISTER(kld_load, sdt_kld_load, NULL,
353 	    EVENTHANDLER_PRI_ANY);
354 	sdt_kld_unload_try_tag = EVENTHANDLER_REGISTER(kld_unload_try,
355 	    sdt_kld_unload_try, NULL, EVENTHANDLER_PRI_ANY);
356 
357 	/* Pick up probes from the kernel and already-loaded linker files. */
358 	linker_file_foreach(sdt_linker_file_cb, NULL);
359 }
360 
361 static int
362 sdt_unload()
363 {
364 	struct sdt_provider *prov, *tmp;
365 	int ret;
366 
367 	EVENTHANDLER_DEREGISTER(kld_load, sdt_kld_load_tag);
368 	EVENTHANDLER_DEREGISTER(kld_unload_try, sdt_kld_unload_try_tag);
369 
370 	sdt_probe_func = sdt_probe_stub;
371 
372 	TAILQ_FOREACH_SAFE(prov, &sdt_prov_list, prov_entry, tmp) {
373 		ret = dtrace_unregister(prov->id);
374 		if (ret != 0)
375 			return (ret);
376 		TAILQ_REMOVE(&sdt_prov_list, prov, prov_entry);
377 		free(prov->name, M_SDT);
378 		free(prov, M_SDT);
379 	}
380 
381 	return (0);
382 }
383 
384 static int
385 sdt_modevent(module_t mod __unused, int type, void *data __unused)
386 {
387 	int error = 0;
388 
389 	switch (type) {
390 	case MOD_LOAD:
391 		sdt_load();
392 		break;
393 
394 	case MOD_UNLOAD:
395 		error = sdt_unload();
396 		break;
397 
398 	case MOD_SHUTDOWN:
399 		break;
400 
401 	default:
402 		error = EOPNOTSUPP;
403 		break;
404 	}
405 
406 	return (error);
407 }
408 
409 DEV_MODULE(sdt, sdt_modevent, NULL);
410 MODULE_VERSION(sdt, 1);
411 MODULE_DEPEND(sdt, dtrace, 1, 1, 1);
412